This invention relates to well cleaning apparatus and, more generally, to apparatus used for the cleaning of the insides of pipes, tubes, liners and the like.
It is considered desirable when drilling for oil or gas to maintain a clean interior in the casing or liner of the drilling well. For this purpose, well cleaning apparatus is well known and comes in a variety of different forms. One such type of well cleaning apparatus is generally known as a casing scraper. This type of tool typically incorporates steel casing scraper blades that scrape the inside of the casing or tubing in the well. A second type of well cleaning apparatus known in the art may be more accurately likened to a brush and incorporates cleaning pads with protruding bristles. Brushing tools are generally used to clean well casings, tubing and the like of smaller debris and or particles than that of scraper tools.
The present invention recognises that these and other clean up tools are not entirely satisfactory in cleaning all areas in well tubing. For example, where threads or joints exist, the inside surface of the tubing may be slightly irregular leading not only to increased entrapment of mud or debris, but the diminished accessibility of known clean up tools. Also, many well cleanup tools are not particularly suited to low tolerances in the tubing ovality.
An object of the present invention is to provide an alternative type of cleaning member on a clean-up tool used in well tubing and the like that provides improved penetration and cleaning in at least certain applications. From the description herein it will be seen that the invention provides other advantages over known art. For example, another disadvantage of the aforedescribed tools is that although they may be relatively efficient at removing particles from the casing wall, they do not necessarily prevent the debris from then remaining suspended in the well fluid even if the fluid is circulated through the well, not all of the debris is flushed out the surface. Thus, even where filters are provided to clean the well fluid, these may not be entirely effective as debris may remain suspended below the surface in the well.
In order to address this deficiency, other tools have been designed and manufactured which are intended to catch and/or trap the debris suspended in the circulation fluid. One example of this type of tool is described in our co-pending British Patent Application No 9806274.8. However, again while such tools mitigate the problem, they are not completely deficient and can also retard circulation in the well.
Accordingly, the present invention results from the additional recognition of a need to provide better apparatus and methodology for cleaning the annulus between a drilling string or work string and a casing string. Indeed, it is an object of the present invention to provide improved apparatus and method for cleaning casing string that is also adapted to clean the annulus between the work string and the casing string. Specifically, an object of the present invention is to remove suspended debris and particles from the aforedescribed annulus.
According to the present invention there is provided well cleaning apparatus comprising a tubular body member adapted for attachment to a work string, the body member supporting one or more resilient and pliable cleaning members biased in an outward radial direction to enable a generally planar surface of the or each cleaning member to contact the well casing or other tubing in use, the one or each cleaning member being made from a foam, polymeric or rubber material, and wherein the apparatus further includes bypass means for selectively enabling the circulation of fluid past the cleaning members when desired.
The cleaning member may be made from an elastomer and more specifically a thick walled polyurethane elastomer.
Preferably, the or each cleaning member is provided in the form of a cup that typically is positioned in a concave down orientation when the apparatus is suspended vertically in a well. Alternatively, the or each cleaning member may be an inflatable bladder.
The cleaning member may co-operate with the body member so as to create the said outward radial bias, in use. For example, the inflatable bladder may be suspended in compression during a cleaning operation between two portions of the body member.
Alternatively, the cleaning member may be formed with an inherent radial resilience that is maintained in radial compression in use.
Preferably, an abrasive and hard wearing surface is provided on the exterior of the cleaning member. Typically, the cleaning member would be manufactured as a composite, with the abrasive surface being adhered or welded to the outer surface of the cleaning member.
Preferably, the or each cleaning member sealably engages the inside wall of the casing or other tubing.
The bypass means may be provided as a rupturable disc or portion within the or each cleaning member. Alternatively, the by-pass means may be formed as a channel in the body member.
Also according to the present invention there is provided a well cleaning system comprising a tool having a tubular body member adapted for attachment to a work string, the body member supporting one or more resilient and pliable cleaning members biased in an outward radial direction to enable a generally planar surface of the or each cleaning member to sealably contact the well casing or other tubing in use, the one or each cleaning member being made from a foam, polymeric or rubber material, wherein the tool further includes bypass means for enabling the circulation of fluid past the cleaning members when desired, and means for closing said bypass, and the body member including a generally axial bore therethrough, wherein the bore communicates with a flow path to the surface of the well via the work string.
The apparatus may be associated with filtration means, that typically may be located at surface.
The apparatus may also be associated with vacuum or sucking means for providing suction of well fluid up the bore through the work string.
According to a second aspect of the invention herein there is provided a method of cleaning a well, the method including the step of running a work string into the well, the work string supporting one or more cleaning members adapted to plunge the well by sealably engaging the well casing such that the majority or substantially all of the well fluid below the one or more cleaning members is caused to flow up a bore or channel provided in the work string to surface.
The method may further include cleaning the well casing wall by the contact of the cleaning members thereon. The contact may be a scrubbing action.
The method may further include sucking the well fluid up the work string using a vacuum system or pump.
The method may further include filtering the well fluid, preferably at surface and thereafter directing the fluid back into the well.
The method may further include pressuring up behind the or each cleaning member so as to rupture a disc to enable fluid bypass after plunging the well.